This invention relates to novel complex block multipolymer surfactants for urethane systems and compositions of polyurethane foams containing such surfactants. More specifically, the present invention relates to a surfactant comprising a hydroxyl terminated polysiloxane, one or more diols and a diisocyanate.
The primary advantage of the present invention resides in the ability to tailor a surfactant for a particular urethane formulation or group of formulations. Specifically, while the siloxane is used for its surface active properties, the diisocyanate is employed as a linking agent for combining the hydroxyl terminated siloxane and the diol or diols forming urethane linking groups.
By choosing particular combinations of isocyanates, alcohols and siloxanes which have particular solubilities in a desired urethane system, a surfactant which will stabilize the foam of that system can be produced. This is particularly desirable in that the isocyanates and alcohols employed in the production of the surfactant can be generic to urethane manufacture and, in many cases, similar or identical components can be used in the manufacture of the surfactant as are used in the urethane formulation to be stabilized. The simple manufacturing procedures involved and the ability to use commercially available components results in a low cost surfactant.
Other advantages of the present invention include:
a. controlling the molecular weight of the surfactant polymer by adjusting the isocyanate to the multicomponent hydroxyl ratio;
b. controlling the molecular weight distribution of the surfactant polymer by adjusting the distribution of raw materials and by modifying the reaction sequences;
c. controlling the surface activity of the product via the amount of siloxane in the product by varying the ratio of siloxane in the multicomponent raw material mix;
d. producing surfactants with only small amounts of siloxane, e.g., in amounts as low as 2.0% by weight polydimethylsiloxane;
e. controlling molecular weight and molecular weight distribution by the addition of monofunctional components;
f. production of a branched surfactant by the addition of components having a functionality of greater than two;
g. ability to utilize amine terminated components in addition to or in substitution for hydroxyl terminated components.
Organosilicone polymers which are useful in the formation of polyurethane foams are disclosed in U.S. Pat. No. 4,022,722 to the Union Carbide Corporation. Said organic polysiloxane surfactants may be generally characterized as a linear alternating block copolymer of a siloxane and a polyoxyalkylene and may be represented by the following: EQU .about.SOSOSOSOSOSOSO.about.
where
S represents ##STR1## and O represents Y--Z--.sub.n Y and wherein PA0 Z is a polyoxyalkylene and PA0 X has reacted with Y PA0 S represents ##STR2## Z is a polymeric or non-polymeric carbon compound I represents O.dbd.C.dbd.N--L--N.dbd.C.dbd.O PA0 L is a polymeric or non-polymeric carbon compound PA0 A represents HO--R--OH where R represents one or more polymeric and/or non-polymeric carbon compounds and the isocyanate --NCO) and hydroxyl --OH) groups have reacted to form urethane linkages. One such reaction may be generally represented by the following: ##STR3## PA0 polyoxyalkylenes(polyalkylene oxides)--polyethers such as polyethylene oxide and polypropylene oxide and/or combinations of same; PA0 grafted polyoxyalkylenes--polymer polyols such as polyoxyalkylene with polystyrene and polyacrylonitrile grafted onto the polyoxyalkylene chain; PA0 polyesters--polybutylene adipate, polycaprolactone, etc; PA0 polybutadienes; PA0 non-polymeric diols--1-4 butane diol, diethylene glycol, dipropylene glycol, etc.; PA0 combinations of the above materials. PA0 MDI (diphenyl methane diisocyanate); PA0 MDI prepolymers--MDI that has been pre-reacted with a polymeric or non-polymeric diol; PA0 modified MDI--a mixture of pure MDI and trifunctional cycloadducts of MDI; PA0 TDI (toluene diisocyanate)--both pure and mixtures of isomers; PA0 TDI prepolymers; PA0 aliphatic diisocyanates--such as hexamethylene diisocyanate.
Said components have been found quite useful in stabilizing polyurethane foams.
In contrast to the linear alternating block copolymer disclosure in the prior art, the surfactants of the present invention may be generally characterized as complex block multipolymers with a total molecular weight of from about 10,000 to 100,000 in which a diisocyanate is used to link together two or more hydroxyl terminated blocks resulting in a multicomponent surfactant with random or semi-ordered arrangement of the hydroxyl terminated blocks depending on the reaction sequence by which the surfactant is made (e.g., prepolymers) and/or the relative reaction rates between the various hydroxyl groups and the isocyanate. Examples of surfactants described by the present invention may be represented by the following: EQU .about.IAIAIAIAISISIAISI.about. EQU .about.ISIAISIAIAISIAIAISISIS.about. EQU .about.SIAIAISISIAIAISISIAIA.about. EQU .about.I(AI).sub.r SI(AI).sub.t S.about.
where
where
The siloxane block is typically a chain of recurring siloxane units and is present in amounts of from 2% to 50% by weight. In a preferred embodiment of this invention, the siloxane is polydimethylsiloxane and the preferable termination contains a carbinol group (C--OH). It should be noted that siloxanes with terminating groups that are themselves polymers can be employed so long as a hydroxyl group is present.
The diol component can be any one or a combination of any number of polymeric or non-polymeric materials chosen so as to have a particular compatibility/solubility in the urethane formulation that is to be ultimately stabilized. Examples of the kinds of materials that can be used include hydroxyl terminated:
Examples of the diisocyanates that can be used in the practice of the present invention, which are also chosen so as to have particular compability/solubility in the urethane formulation to be stabilized, include:
The listings above should not be regarded as limiting by omission the materials that may be used. In the practice of this invention, monofunctional components may be used to control the molecular weight and distribution, and components with functionalities greater than two may be used to provide branching.
Amine terminated materials may be used in substitution for or in addition to the hydroxyl terminated materials. The amine group reacts with isocyanate to form urea linkages. This may be generally represented by the following: EQU RNCO+R'NH.sub.2 .fwdarw.RNHCONHR'
In carrying out the process of the present invention, it is generally preferred that the components be mixed together at about room temperature and pressure. The following examples are provided to illustrate the present invention and are not to be regarded as limiting upon the scope thereof.